Since we cannot use PowerShell for everything, it is also possible to execute a certain set of functions inside ARM templates. These can be very useful; for example, they can be used to generate a unique string for certain resources, to concatenate variables and parameters, and much more.

The function uniqueString will deterministically generate seemingly unique strings, depending on the seed that you are using. This function should by no means be seen as a cryptographic hash function. For our intents and purposes, this function generates random strings that can be concatenated with strings fitting your own naming scheme, for example. Take a look at the next code sample to see the template functions in action:

$template.variables = @{
    # Two functions at once. Concatenate contoso with a
    # unique string. The hash function uniqueString requires a seed
    # which is our resource group GUID
    storageAccountName = "[concat('contoso', uniquestring(resourceGroup().id))]"
}

# Export and deploy again
$template | ConvertTo-Json -Depth 100 | Out-File -FilePath .StorageAccountFunctions.json -Encoding UTF8

$deployment = @{
    Name = 'ThirdDeployment'
    ResourceGroupName = $resourceGroupName
    TemplateFile = '.StorageAccountFunctions.json'
    Verbose = $true
}

# Use your template parameters in the resource group deployment!
New-AzureRmResourceGroupDeployment @deployment -location 'westeurope' -storageAccountType 'Standard_LRS'